registered by the overmen three times a day;
it being well known that a diminution of
atmospheric pressure would allow the gas to escape
more readily from the "goaf" into the workings.
Hence when there is a sudden fall in the
barometer, the overmen are more careful and
watchful than on ordinary occasions. And
the evidence of the miners confirms that of the
viewers. They almost invariably state that
all has been done which science could suggest
or forethought devise. Yet, from some
unexplained or unexpected cause, a blast takes
place, and numbers of men and boys are
hurried in a moment into eternity. After the
misfortune the pit is closely examined by
viewers from distant parts. No fault can be
found with the ventilation; eighteen or twenty
thousand cubic feet of air pass through the
workings in the space of one minute, and
all is mystery as to how the explosion took
place, except it had been traced to the
carelessness of some of the workmen. This
is the oft-repeated testimony given before the
coroner. A verdict of " accidental death"
is returned, or sometimes the gas was
suspected to have fired at one of the men's
candles, which party was of course certain
to have been killed, and there the matter
ends.

All this proves very clearly that something
more is required for safety, and that other
precautions than those usually adopted are
needed to stop the invasion of the death-
dealing blast, and no less dangerous and insidious
after-damp, which too surely follows
the track of the fire, and completes what the
explosion may have left unfinished.

It may be necessary for the information of
some of your readers to explain the method
of working pits in Northumberland, and Durham.
In large collieries there are generally
two shafts—a down-cast and an up-cast shaft.
In the former, the air descends into the workings,
is conducted along the main air-course
to the different parts, and is finally expelled
by the up-cast shaft. There is a furnace
continually burning to keep the current in
circulation, which is of considerable importance;
for if it was stopped, the air would remain in
the workings, but would not be renewed, and
therefore become charged with gas. There
are two parts of the mine, called by the names
of the " whole " and the " broken." The
broken is the most dangerous portion, being
the spaces from whence the coal has been
abstracted in the form of chambers, leaving
pillars standing at intervals to support the
roof. In the latest method of working, there
are vacant spaces left which are called " goafs,"
and in which the gas accumulates. This gas
being carburetted hydrogen is much lighter
in specific gravity than common air, and has
a tendency to rise to the roof of the mine.
This tendency is taken advantage of, and
goafs are constructed in particular portions
as reservoirs. The form of the goaf is that
of the interior of a dome. For the sake of
illustration, I will suppose it will be similar
to an inverted water bowl, the gas being
collected in the inside, and prevented from
escaping by the pressure of the atmosphere
round the edges. It is also found that if a
certain quantity of air can be driven through
the mine, even should there be a small escape
of gas from the goaf, it will do no harm, provided
it is diluted with air below the explosive
point. Now here is the theory of working:
if a good current of air be maintained, and
Davy Lamps are used in dangerous places
with properly stopped trap-doors, an
explosion cannot happen, as the lamp gives
certain indications of the presence of gas,
which, if properly attended to, warn the miner
that he ought to retire. From the unanimous
evidence of the viewers it appears that no
explosion has ever been traced to a properly-
constructed Davy lamp, but in spite of all
this they are continually taking place from the
proximity of naked lights in parts where
candles are prohibited; and it therefore
becomes a question whether some means could
not be devised for carrying off the greater
portion of the gas from the goafs—at least so
much as to keep them under control—and
disposing of it in a manner which would
render it harmless. It is frequently given in
evidence that the men are careless, and, trusting
to the measures adopted by the viewers
for safety, are too apt to conclude that they
are perfectly safe, when it must occur to
every reflecting mind, that even supposing
the viewers have done their duty—and I
believe the present viewers are, as a body, well
grounded in science—the work is but half
performed, if the men do not second the
efforts of their directors by carefulness and
vigilance. A dozen viewers might recommend
particular systems, each of which would
be safe; but one man may overturn all their
precautions, and cause an accident, to prevent
which hundreds of pounds may have been
expended.

It will be evident, without further proof,
that the only certain method will be to rid
the mines of those magazines of gas as far as
is practicable. I call them " magazines,"
because they are just as dangerous in the
vicinity of candles as a magazine of gunpowder
would be. In the Houghton pit—where a
late explosion took place by the gas firing at
a naked light, and by which twenty-seven
lives were lost—has four goafs; two of
eighteen acres each in extent, one of seven,
and one of four acres. Just imagine eighteen
acres of combustible gas, ready to fire the
moment that it received a certain mixture of
atmospheric air! and the only wonder is that
explosions are not still more frequent.

Now, I conceive that the greater portion
of this gas might be discharged. The very
essentials for such a process are half
completed to our hands. These goafs are
immense domes, brim-full of explosive gas, though
in an inverted position. It cannot explode